THE CROSS-BREEDING OF RACES 141 



"mongrels") tell of an interesting suggestion made to 

 me by my friend Professor Alphonse Milne-Edwards 

 not long before he died, and never published by him. He 

 was director of the Jardin des Plantes in Paris, where 

 there is a menagerie of living beasts as well as a botanic 

 garden and great museum collections and laboratories. 

 He held it to be probable, as many physiologists would 

 agree, that the fertilization of the egg of one species by 

 the sperm of another, even a remotely related one, is 

 ultimately prevented by a chemical incompatibility 

 chemical in the sense that the highly complex molecular 

 constitution of such bodies as the anti-toxins and serums 

 with which physiologists are beginning to deal is 

 "chemical" and that all the other and secondary 

 obstacles to fertilization can be overcome or evaded in 

 the course of experiment. He proposed to inject one 

 species by " serums " extracted from the other, in such 

 a way as seemed most likely to bring the chemical state 

 of their reproductive elements into harmony, that is to 

 say, into a condition in which they should not be actively 

 antagonistic but admit of fusion and union. He proposed, 

 by the exchange of living or highly organized fluids (by 

 means of injection or transfusion) between a male and 

 female of separate species, to assimilate the chemical 

 constitution of one to that of the other, and thus possibly 

 so to affect their reproductive elements that the one could 

 tolerate and fertilize the other. The suggestion is not 

 unreasonable, but would require a long series of experi- 

 ments in which the possibility of producing such " assimi- 

 lation," even to a small extent and in respect of less 

 complex processes than those ultimately aimed at, would 

 have to be, first of all, established. My friend did not 

 live to commence this investigation, but it is possible that 

 some day we may see the obstacle to the union of ovum 

 and sperm of species, which are to some extent allied, 



